Choosing switches for a sim racing button box

The switches decide most of how a button box feels to use. A mushy switch, or one that's easy to bump by accident, gets annoying over a long stint. These are the things to think about before you buy forty of them.

Linear, tactile or clicky

Keyboard-style switches like Cherry MX and their copies come in three kinds.

• Linear switches go straight down with no bump. Smooth and quiet. Cherry MX Red and Black are the usual examples.
• Tactile switches have a small bump partway down, so you can feel when it's pressed. MX Brown is the common one.
• Clicky switches have the bump plus a click you can hear. MX Blue is the classic. Great feedback, but your mic will pick it up if you stream or talk on team comms.

For a button box, tactile is a good middle ground. You can feel each press without looking down, which matters when your eyes are on the track.

How heavy

Switches are rated by how much force it takes to press them. A Cherry MX Red is about 45 cN and a Black is about 60 cN. On a rig, a heavier switch is harder to press by accident when you reach past it or brush it with your hand. For buttons you really don't want to hit by mistake, go heavier, or use a different kind of control altogether.

Momentary, latching, and the other kinds of controls

MX switches are momentary: they're only on while you hold them. That's what games expect for most functions. A few things are better as something else:

• Rotary encoders for anything you step through: brake bias, traction control, ABS, fuel mix. Each click is one step up or down, and they spin forever, so they never get out of sync with the car.
• Toggle switches with flip covers for ignition and starter. The cover means you can't kill the engine with your knee.
• Multi-position rotary switches for modes with a fixed number of settings.
• Big arcade buttons for anything you press a lot with gloves on, like pit limiter or push to talk.

Keycaps and labels

Cherry MX style switches take keycaps with a cross-shaped stem, so there's a huge choice, and they're easy to print. Label them, because in the middle of a race it's hard to remember which unmarked button was wipers. Printed legends or labels you can read in a dark room save a lot of wrong presses.

Wiring and the board

Every switch needs an input on a controller board, and the board is what Windows sees as a game controller. Two common options:

• A USB encoder board, the kind sold for arcade sticks. Wire each button to its own input and it works with no programming.
• An Arduino Pro Micro, or another board that can act as a USB game controller. More work, but you can do anything, including encoders and LEDs.

Count your inputs before you choose. An encoder uses two inputs, plus a third if it has a push button. Sixteen buttons and four encoders is already 24 to 28 inputs, which is more than a Pro Micro has pins for. The usual way around that is a button matrix: buttons wired in rows and columns with a diode on each one, so pressing two at once doesn't register as a third.

A starting point

If you're not sure, this layout suits most people:

• Tactile switches for the main buttons.
• Encoders for brake bias, TC and ABS.
• One covered toggle for ignition.
• Labelled caps.

After a week of racing with it, you'll know what you want to change.

I'm building a button box along these lines: 16 Cherry MX switches, 4 encoders and printed keycaps, mounting to 4040 extrusion. It isn't for sale yet. If you want to hear when it is, email support@builderlab3dp.com.